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An analysis was conducted of the community structure variability of demersal fish larvae and its relationship with environmental forcing on the west coast of the Baja California Peninsula (25–31°N). The information comes from two data sets of oceanographic cruises in 1997–2000 and 2006–2010. From a total of 190 identified taxa, a high number of species (71) was shared throughout the peninsula. The spatiotemporal contrast in the community structure suggests the separation of two groups (northern and southern) whose boundary is located around Punta Eugenia. The northern group showed an alternate dominance of species with a subarctic-transitional faunistic affinity during the winter and spring and species of a subtropical affinity during summer–autumn. In contrast, the dominant taxa in the southern group have a tropical–subtropical affinity throughout the year, although some taxa of subarctic-transitional affinity also occur during winter–spring. In the spatiotemporal scale, these results suggest that the major cause that modulates the extension and structure of the assemblages is the seasonal oceanic dynamics. Moreover, the intensity of warming or cooling events (El Niño and La Niña) influences the structure of the community on an interannual scale by displacing the zonal boundaries of the groups’ distribution. [ABSTRACT FROM AUTHOR]

The aim of this work was to determine if the variation patterns in the abundance of dominant species of fish larvae in the transition zone off Bahía Sebastián Vizcaíno, Mexico, could be used as indicators of interannual environmental variability, and how larval fish assemblages respond to this environmental variability during the period 1997–2013. With the 16 years of plankton data in the southern region of the California Current System, anomaly curves of larval abundance were calculated, from which the temporal abundance patterns of the dominant fish larvae of the mesopelagic, epipelagic and demersal environments were obtained. Classification and ordination analyses were carried out to obtain the larval fish assemblages as well as their relations with environmental variables (sea surface temperature, surface salinity, concentration of Chlorophyll-a and zooplanktonic volume) and climatic indexes (ONI, MEI, PDO and NPGO). Results showed a high positive correlation between the mesopelagic abundance with MEI and PDO indices, demonstrating their affinity with warm oceanic waters, while there were not statistically significant correlation between the climatic indexes and the epipelagic (Sardinops sagax and Engraulis mordax) or demersal species (Synodus lucioceps). The interannual variability of the abundance of three dominant mesopelagic species (Vinciguerria lucetia , Diogenichthys laternatus and Cyclothone signata) show that these species had a clearer response to environmental variability than epipelagic and demersal species. Trends in the abundance of mesopelagic species larvae and their high correlation values with the environmental variables used, demonstrate their potential as indicators of environmental change of the pelagic ecosystem in the transitional area off Bahía Sebastián Vizcaíno. [ABSTRACT FROM AUTHOR]

Vinciguerria lucetia is a mesopelagic fish whose larvae show an almost permanent presence in the southern portion of the California Current System. Due to its sensitivity to environmental changes, the species has been considered an indicator of water masses and interannual variability. Fish larvae abundance registered from 1997 to 2015 by the program Investigaciones Mexicanas de la Corriente de California was used to predict the abundance distribution of V. lucetia larvae under two extreme thermal conditions (2000 La Niña and 2015 El Niño), utilizing the novel machine learning algorithm eXtreme Gradient Boosting (XGBOOST). The data were segmented into COLD and WARM groups based on the mean sea surface temperature recorded at each station and contrasted with an undivided TOTAL group. Models were generated using 12 environmental and biological predictor features. Root-mean-squared logarithm error (RMSLE) was used as a prediction performance metric for both internal and external validation. The COLD model showed the best performance for the internal validation with a lower RMSLE value, while the TOTAL model for both the coldest and warmest external validation presented the lowest RMSLE values. The external validation demonstrated models that accurately predicted the spatial distribution; however, none of the models were able to accurately predict the same abundance magnitude observed in both extreme thermal conditions. Nevertheless, XGBOOST shows promise for describing the future distribution traits of V. lucetia. [ABSTRACT FROM AUTHOR]

The distribution of ichthyoplankton assemblages (summer 1999 and winter 2000) from the southern region of the California Current (CC) off the Baja California Peninsula were analyzed. Latitudinal and ocean-coast distribution limits of the assemblages were associated with the geostrophic flow, which showed the presence of cyclonic and anticyclonic eddies in the northern and central region of the Baja California Peninsula. The comparative analysis of distribution and abundance of the developmental stages (egg to preflexion, flexion, and postflexion larval stages), showed that each mesoscale eddy had a specific ichthyoplankton assemblage, and the ichthyogeographic regionalization of the study area was determined by the presence of eddies and fronts. Retention processes were observed on epipelagic and demersal species where the fish larvae were maintained near the coastal region. [ABSTRACT FROM AUTHOR]